Production of distillate



21, 4 w. M. s TlATFoRo 2,363,207

PRODUCTION OF DIS'IILLA'I'E Filed May 8, 1941 comPazssoa SEPEBATOE faETTLEE urkrea' WILLIAM M 5T BAT F0 20 J INVENTOR Patented Nov. 21 1944 UNITED STATES PATENT OFFICE PRODUCTION or DISTILLATE William M. Stratl'ord, New York, N. Y assignor, by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application May 8, 1941, Serial No. 392,538 7 Claims. (01. Isa-+1145) This invention relates to a process for the production of distillate reservoirs wherein liquefiable hydrocarbons are recovered from the fluid flowed from a well tapping a reservoir of this type, and residual gases are preferably returned to the same or a different distillate reservoir for the. purpose of maintaining formation. pressures.

It is the principal object of the invention to provide a novel and efficient process for the recovery of liquefiable hydrocarbons from distillate fluids which possesses important advantages over the processes heretofore proposed for thislpurpose.

Other objects of the invention will in part be obvious and in part will appear hereinafter.

In the production of hydrocarbons from a distillate reservoir, it is recognizedthat in order to prevent the condensation of liqueflable hydrocarbons in the reservoir itself, which results in per.- manent loss of hydrocarbons, the residual gases should be returned to the reservoir so as to avoid as far as possible any drop in-pressure in the formation. The fluid flowed from a well tapping a distillate reservoir is under such conditions of temperature and pressure that the fluidexists substantially as a homogeneous gas phase.

The temperatures of typical distillate fluids at the well head are of the order of 125 to 175 F. and the pressures are of the order of 1500 to 5000 pounds per square inch or above. A reduction in the pressure of this fluid causes condensation of hydrocarbons. Accordingly, most of the processes which have been employed for the recovery of hydrocarbons from distillate fluids have involved as an essential feature materially reducing the initial pressure of the fluid. Because of the necessity of returning the residual gases to the formation under pressuresexceeding the formation pressures, the reduction in pressure above ground has added materially to the costs of the processes.

Absorption processes using a relatively heavy absorption oil have also been employed. These processes have involved a single stage oil absorption carried out at a pressure below 2,000 pounds per square inch in which, after cooling the distillate fluid from its initial temperature to a lower temperature considered desirable for'absorption, the fluid is passed into contact with a\ abs'orption oil to absorb. liquefiable hydrocarbons and yield residual gases which are compressed I and returned to the formation.

In considering the conditions under which processes for the recovery of liqueflable (i. e. normally liquid) hydrocarbons from distillate fluids are carried out, it is of advanta e to keep in mind the phase relations of the fluids. For a discussion of phase relations see the article, "Retrograd condensation, by D. L. Katz and F. Kurata, Industrial and Engineering Chemistry, vol. 32, No. 6, June 1940, pages 817-827. In the reservoir a distillate fluid is considered to exist as a single phase and the conditions at which the fluid is flowed from a well are usually somewhat within the two phase boundary on the temperature-pressure plane. Thus the temper-' atures in the reservoir and at which the fluid is flowed from the well are above the temperature at the critical point for the fluid, and the pres- 16 sures on the fluid in the reservoir and when the fluid is flowed from the well are usually not substantially below the Pressure of the two-phase boundary at the existing temperature. It will be understood that where the conditions of tem- 20 perature and pressure of a distillate fluid are near thetwo-phase boundary in the critical area, raising the temperature and/or pressure serves to move the conditions away from the two-phase region; i. e., away'from conditions at which condensation of-liquid takes place.

In accordance with the present invention the fluid flowed from a well tapping'a distillate res-' ervoir is intimately contacted with a medium consisting essentially of water to remove liqueflable hydrocarbons from the fluid and leave residual ases which are preferably returned at least in part to a distillate reservoir for the purpose of maintaining formation pressures. The contact between the fluidand the medium may be and preferably is accomplished at a pressure not substantially below well head pressure. Also the temperature" during the contact may be maintained substantially atthe temperature. at which the fluid is flowed from the well, somewhat below this temperature, although preferably not sufliciently low to permit the formation of hydrates, or at an elevated temperature. The-temperature at which the operation is carried out has an efiect on the solvent action of the water.

The advantages of proceeding as described above are more or less apparent. As compared with absorption processes, the process has the advantage that inexpensive water rather than an absorption oil is used, and also, whereas absorption processes are'preferably carried out at a at Which the fluid 'is flowed from the well, the process does not require cooling. As compared with the so-called retrograde condensation processes, in which cooling and a reduction in prestemperature substantially below the temperature sure are elied upon for causing condensation, the proces has the advantage that cooling is not required and it may be carried out at substantially well head pressures or higher pressures. The residual gases, therefore. are obtained in any case at a pressure only slightly below well head pressures. This is, of course, a distinct advantage where the residual gases are to be returned to a distillate reservoir, which is the usual situation.

As pointed out above, the temperature of the fluid flowed from a distillate well may vary from in the neighborhood of 125 to 175 F., and the present process may be carried out at temperatures of this order. The process may also be carried out, however, at elevated temperatures;

for example, at temperatures above 200 F. and

especially at a temperature within a range of 400 to 600 F. The distillate fluid and the aqueous medium, will ordinarily be at substantially the same temperature at the time of bringing theminto contact,- but in certain cases the temperature of the fluid may be somewhat below the temperature ofthe medium. p

In addition to water the essentiall aqueous solvent employed in the present process may coneral the synthetic detergents are characterized by containing a straight or branched alkyl chain of at least 8 and preferably 12 to 16 carbon atoms and a solubilizing group such as a sulphate or sulphonate group and are usually employed in the form of the alkali metal, including ammonium, preferably sodium, salts. Detergents of this type are represented by the products marketed under the trade names, Nacconol, Gardinol, and Igepon.

tain additives which upon admixture with water produce a solution adapted to dissolve or absorb hydrocarbons containing four or more carbon atoms at elevated temperatures and pressures. These additives also preferably are such as to produce a solvent mixture in which hydrocarbons containing four or more carbon atoms are relatively insoluble at low temperatures As additives for this purpose there may be mentioned hydroxy and polyhydroxy organic compounds which are substantially completely soluble in water at least at elevated temperatures. Representative examples of compounds of this class are dihydroxy saturated and unsaturated alcohols such as ethylene glycol, polyethylene glycols, trimethylene glycol, butylene glycol, and polyolefln glycols; halogenated derivatives of the'di-- hydroxy alcohols such as trimethylenechlorhydrin, glycerol alpha and beta dichlorhydrins, and ethylene chlorhydrin; alkyl ethers of the glycols such as ethylene glycol mono methyl ether and ethylene glycol diethyl ether; alcohols such as ethyl alcohol, poly-vinyl alcohol, and allyl alcohol; poly-hydroxy alcohols such as glycerine,

to which has been added an agent adapted toreduce the surface tension of the water, or a solvent mixture of the type discussed above containing in addition an agent for reducing the surface tension. Agents for reducing surface tension of water are well known and comprise,

for example, compounds such as water-soluble soaps (e. g. alkali metal oleates), and synthetic wetting agents and detergents, examples of which are alkyl aryl sulphonates, alkyl sulphates, and estersand amides of higher fatty acids with lower sulphonated alcohols and amines. In gen- In order that theinvention may be understood more fully reference will be made to the accompanying drawing in which is illustrated one manher of operating the present process.

Referring to the drawing, a distillate fluid is flowed from output well A, which taps a distillate reservoir, through valved line In leading to a heat exchanger II. In this heat exchanger the fluid is brought into indirect heat exchange relationship with the relatively hot fluid flowing in line 32, as will presently be described. From the heat exchanger the fluid flows through a heater l2. As noted above, distillate fluids are normally removed from the well at a temperature in the neighborhood of 125 to 175 F. and at an elevated pressure, the conditions of temperature and pressure together being usually not substantially within the two-phase boundary for the fluids on the temperature-pressure plane. In accordance with this embodiment of the invention the fluid is heated in the heat exchanger and heater to a temperature above 200 F., for example, a temperature within the range of about 400 to 600 F. From the heater, the fluid passes through line H leading to a mixing tower l6. Water is introduced into the fluid flowing in line Id through line I8, the water being at about the same temperature as the fluid. The amount of water used may vary, but ordinarily will be used in considerable excess; For example, the aqueous medium may be used in proportions corresponding to a liquid volume ratio of medium to hydrocarbons which it is desired to absorb of 20:1 to 200-:1 or

more.

After the introduction of water, the mixture of the distillate fluid and water flows into the lower portion of mixing tower Hi. This tower is preferably provided with means, such as Raschig rings 2|], for inducing intimate contact of liquid and gases. The mixture then flows from theupper portion of mixing tower l6 through line 22 to a separator 24. In the separator, which is preferably provided with baiiles at least in the upper portion thereof, a separation is accomplished between residual, undissolved gases, largely gases composed of hydrocarbons having three or less carbon atoms, principally methane, and an aqueous phase consisting of the water and dissolved or absorbed hydrocarbons. The residual gases are removedfrom the top of tower 24 through line 26 leading to a compressor 28. The compressor serves to raise the pressure on the residual gases to a sufiiciently high point to return them to the distillate reservoir tapped by well A, through valved line 30 and input well B.

The hot aqueous fluid is removed from separator 24 through line 32 leading to heat exchanger II where the aqueous fluid gives up part of its heat tothe incomin well fluid. From the heat exchanger, the aqueous fluid passes into line 33 leading to a cooler 34. In this cooler the'temperature is reduced to a sufiiciently low point to.

the middl portion of a settler 36 wherein the liquid is rmitted to settle and separate into an aqueous and a hydrocarbon phase. The hydrocarbon phase is removed from the upper portion of the settler through valved line 40 leading to a flash tank 42 wherein the pressure on the hydrocarbon mixture is reduced to about 500 poundsper square inch. Gases formed due to this reduction in pressure are removed from the top of the tank through valved line 44. These gases, by

means not shown, are preferably used for heating the fluid passing through heater l2. Any water settling out of the hydrocarbon mixture in this tank may be removed throughvalved line 46.

From tank 42 the hydrocarbons are passed the heater 60 which is operated to raise the temperature of the medium to about the temperature of the fluid flowing in line l4 and the heated medium then passes into line l8 for reuse in the treatment of the distillate fluid. Water make-up may be introduced into the system through valved line 62.

It will be understood that the above described manner of operating may be varied. For example, the process may be operated by maintain-- ing a body of water and passing thefluid therethrough. In this case, an aqueous mixture. of I water and dissolved or absorbed hydrocarbons is continuously removed from the contact zone, hydrocarbons are separated, and the-water is recylcled to the top of the contact zone, resulting in a counter-current contact process. Also, while an operation has been described in which the pressure on the aqueous mixture separated from the residual gases is maintained substantially at the pressure of the fluid, the pressure on this mixture may be reduced to aid in the separation of the dissolved or absorbed hydrocarbons. Further, the hot fluid leaving separator 24 may be brought into heat exchange relationship with the aqueous medium leaving settler 38 to raise the temperature of the water and cool the fluid,

. rather than being used to heatthe incoming well is materially below 3,000 pounds per square inch.

In cases of this type, usually no compression of the residual gases is necessary for returning them to the formation.

The present process may be applied to the treatment of a distillate fluid which is flowed from a distillate well at a' temperature of about 140 F.

p q 3 the major portion of the hydrocarbons containing four or more carbon atoms.

Since changes may be made in the process described above without departing fromthe scope of the invention, it is intended that the description shall beinterpreted as illustrative and not in alimiting sense.

I claim:

1. The process of recovering heavier, liquefiable hydrocarbons from a hydrocarbon mixture flowed at a high temperature and pressure from a well tapping a distillate reservoir, which comprises passin hydrocarbons of said mixture under high temperature and pressure'conditions within the critical region for said hydrocarbons and such that the hydrocarbons are substantially entirely in a single homogeneous gas phase into intimate absorbing relationship with an essentially aqueous medium having solvent properties for the desired hydrocarbons under said high temperature and pressure conditions, to remove a substantial proportion of the heavier, liquefiable hydrocarbons and leave the greater part of the remainder of said hydrocarbons in said homogeneous gas phase.

2. The process of recovering heavier, liquefiable hydrocarbons from a hydrocarbon mixture flowed at.a high temperature and pressure from a well tapping a distillate reservoir, which comprises passing hydrocarbons of said mixture under high temperature and pressure conditions within the critical region for said hydrocarbons, the temperature being above 200 F. and the temperature and pressure together being such that the hydrocarbons are substantially entirely in a single homogeneous gas phase, into intimate absorbing relationship with. an essentially aqueous medium having solvent properties for th desired hydrocarbons under said hightemperature and pressure conditions, to remove a substantial proportion of the heavier, liqueflable hydrocarbons and leave the greater part of the remainder of said hydrocarbons in said homogeneous gas phase.

3. The process in accordance with claim 2 in which the temperature at which the hydrocarbons of said mixture are passed into intimate ab-' sorbing relationship with the essentially aqueous medium is within the range of 400 to 600 F.

4. The process of recovering heavier, liquefiable hydrocarbons from a hydrocarbon mixture flowed at a high temperature anda pressure above 1500 pounds per square inch from a well tapping :a distillate reservoir, which comprises passing hydrocarbons of said mixture under high temperature and pressure conditions within the critical region for said hydrocarbons, said temperature being above 200 F. and said pressure above 1500 pounds and a pressure of about 2600 pounds per square l inch. The fluid according to analysis has the following composition in terms of mol per cent of components: methane 89.46, ethane 3.13, propane 1.56, isobutane 0.74, n-butane 0.89, isopentane 0.37, n-pentane 0.48, and hexanes plus 3.37. The condensate recovered from this fluid will contain persquare inch, said temperature and pressure;

together being such that the hydrocarbons are substantially entirely in a single homogeneous gas phase, into intimate absorbing relationship with an essentially aqueous medium having solvent properties for the desired hydrocarbons under said high temperature and pressure conditions, to remove a substantial proportion of the heavier, liquefiable hydrocarbons and leave the greater part of the remainder of said hydrocarbons in said homogeneous gas phase.

5. The process in accordance with claim 4 in which the temperature at which the hydrocarbons of said mixture are passed into intimate absorbing relationship with the essentially aqueous medium is within therange of 400 to 600 F.

6. The process of recovering heavier, liqueflable hydrocarbons from a hydrocarbon mixture flowed at a high temperature and a pressure above 1500 pounds per square inch from a well tapping a distillate reservoir, which comprises passing hydrocarbons of said mixture under high temperature and pressure conditions within the critical region for said hydrocarbons, said temperature being above 200 F. and said pressure being above 1500 pounds per square inch, said temperature and pressure together being such that the hydrocarbons are substantially entirely in a single homogeneous gas phase, into intimate absorbing relationship with an aqueous 'medium comprising a hydroxy-organie compound soluble in water at said high temperature, said aqueous medium having solvent properties for the heavier, liquefiable hydrocarbons under said high temperature and pressure conditions, to remove a substantial proportion of the heavier, liquefiable hydrocarbons and leave the reater part of the remainder of said hydrocarbons in said homogeneous gas phase.

7. The process of recovering heavier, liquefiable hydrocarbons from a hydrocarbon mixture flowed distillate reservoir, which comprises passing hydrocarbons of said mixture under high temperature and pressure conditions within the critical region for said hydrocarbons, said temperature being above 200 F. and said pressure being above 1500 pounds per square inch, said temperature and pressure together being such that the hydrocarbons are substantially entirely in, a sin 1e homogeneous gas phase, into intimate absorbiEg relationship with an aqueous medium comprisi g an agent for reducing the surface tension of water,

said aqueous medium having solvent properties for the heavier, liquefiable hydrocarbons under said high temperature and pressure conditions, to

remove a substantial proportion of the heavier,

liquefiable hydrocarbons and leave the greater part of the remainder of said hydrocarbons in 

